Your neighbor doesn't currently have the right to do anything they want with their property though. They don't absolutely own it and have some kind of sovereign status. They can't turn it into a gas station or auto repair shop. They have the right to exclusive use of the land for the purpose of a single family dwelling built to certain specifications and abiding by various guidelines and regulations.

When each neighbor bought into the neighborhood, they all signed up for this same basic deal. Many of them would likely have chosen to not spend their money on the property had their neighbors not been bound by the same rules.

What is being proposed is a significant change to those rules that every owner at some point agreed to. This absolutely does affect everyone in the neighborhood because an older neighborhood is more than a collection of unrelated properties, it is a collection of actual homes of similar size and character with a particular feel and aesthetic.

A change to the rules may absolutely be necessary for the health of the city / population as a whole. Totally agree with this. Don't pretend though that it's not coming at the cost of infringing on the existing homeowners' reasonable expectations of what they bought into when they purchased their properties. Again, maybe it does need to happen, but homeowners are not unreasonable for wanting to keep their neighborhoods as they've always known and loved them.